Method and sample extractor for the extraction of intact fluid samples

ABSTRACT

The extraction of intact, representative fluid samples in well-defined depths, such as from wells sunk into the ground, has until now been very difficult, and in many cases impossible to perform. A method is provided as well as a sample extractor for the extraction of intact fluid samples, in particular from a well ( 26 ) sunk into the ground, by submersion of a compressible hollow flexible body ( 22 ) fitted in a supporting device which, subsequent to submersion to the sample extraction depth, is acted upon to effect liquid entry through an inlet. In particular, hollow flexible body ( 22 ) is held in the support device in the form of a pressure vessel ( 2 ) and fully compressed by pressurized gas inside the pressure vessel, whereupon the pressure vessel is caused to change in such a way that a surrounding fluid seeps into the hollow flexible body ( 22 ), whereupon the vessel ( 2 ) with the body ( 22 ) containing the fluid sample is hoisted out of the well ( 26 ).

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a method for the extraction of intact liquidsamples, in particular, from a well sunk into the ground, by submersionof a compressible hollow flexible body fitted in supporting means which,subsequent to submersion to the sample extraction depth, is acted uponto effect liquid entry through an inlet, as well as a sample extractorfor performing the method.

2. Description of Related Art

Such a sample extractor is known from U.S. Pat. No. 4,461,186 whichcomprises a sterile flexible body in the form of a tubular bag, theopenings of which are fitted by means of compression rings to two rigidendpieces, the upper of which comprising an inlet being releasablyfitted to the console of a sample extractor, and the lower being fittedin the vertically displaceable console of the sample extractor which isforced away from the upper endpiece by elastic means. The lower endpiececomprises a vertical pin projecting up into the bag volume and fittinginto said inlet in such a manner that the endpieces are placed at acertain distance from another in the starting position, corresponding tothe length of the pin, whereby air will be present in the bag at thecommencement of sample extraction.

The inlet in the upper endpiece is covered by a hose which is connectedto a glass tube fixed in a crunching mechanism. The sample extraction isactivated in that a weight is dropped when the sample extracted with abag fitted is placed at the desired depth, said weight falling on thecrunching mechanism which fractures the glass tube whereby the inletopening is uncovered, and liquid may flow through it. The same mechanismis further connected to a release mechanism which releases the lowerendpiece so that this, due to the influence of the downward directedelastic means, is displaced such that sample material is sucked throughthe inlet in the upper endpiece. The sample extraction is terminated inthat the lower endpiece acts on a spring loaded valve via arod-and-spring which blocks the inlet in the upper endpiece.Subsequently the sample extractor is hoisted up and the fluid samplecollected in the bag volume may be removed from the sample extractoralong with the endpieces. The sample extraction hence occurs using thebellows principle, where an elastic influence on one endpiece away fromthe upper, fixed endpiece causes surrounding fluid to be sucked into thebag volume.

This known sample extractor would be adapted to use in extraction ofsamples in predetermined depths where the requirements for the methodused are not particularly rigid, i.e., where it is known beforehand thatthe subsequent results of analyses are reasonably removed from thedetection limit of the substances in question. Examples might be theextraction of water samples in marine areas in the sea or in lakes, andin wells and large-diameter wells, where sufficient room is availablefor the submersion of the complete sample extraction equipment.

The extraction of fluid or water samples in order to detect substancesendangering the environment in the course of evaluation of, e.g., theextent and distribution of ground water pollution is commonly performed.The extraction of the water samples directly at the filter of a well aswell as in the water claiming area, where the water samples areextracted in pipes placed in the ground for this purpose.

Since the concentrations of the substances endangering the environmentin, e.g., drinking water wells and water claiming areas are often nearthe detection limit, it is of a large importance that the samples areextracted in such a way that it is representative of the actual waterquality in a given level at the particular sample extraction site.

Hence rigid requirements are put on the cleanliness of the equipmentused for the sample extraction, while it is of a large importance thatthe samples may be extracted in different depths in the well, such thatthese are representative, and to enable the extraction of samples whichare non-oxidised and which have not been subjected to atmospheric air,whereby gasses which may have been dissolved in the water sample mightescape.

It would be impossible to use the sample extractor described in U.S.Pat. No. 4,461,186 for the extraction of the mentioned intact liquidsamples which have to be analysed for substances occurring inconcentrations very close to the detection limit. There are severalreasons for this, e.g., atmospheric air will be present in the bagvolume at commencement of the sample extraction. Lowering of thesampling equipment will cause turbulence and mixing of layers possiblyoccurring within the well, due to the construction and size of theequipment. This situation is further aggravated by dropping weight inorder to crunch the glass tube which initiates the sample extraction.

Alternatively intact water samples may be extracted by means of a vacuumpump situated on the ground by the well, which sucks the water sampleinto a sample bottle. However, it may be difficult to determine theprecise depth from which the sample is pumped, and there may be doubtsas to possible contamination by substances present in the higher waterlayers in the well. Furthermore, there remains the fact that the pumpedwater sample cannot avoid, however briefly, to be in contact with airwhen it is fed to a sample container, which is undesired as describedabove. The problem with using a vacuum pump is furthermore that ithardly functions at depths exceeding 10 m. However, in order to solvethis problem, pumps are known which are so small that they may be sunkinto the well and pump the samples up. If such a pump is to be used inother locations, it must be cleaned first which is a time consuming andhence cost creating work which sometimes makes one use one pump per wellwhich is costly in acquisition but often necessary, but even hereremains the problem of the sample's contact with air.

SUMMARY OF THE INVENTION

It is the purpose of the present invention to provide a method for theextraction of intact fluid samples, in particular from a well sunk intothe ground, by submersion of a compressible hollow flexible body fittedin supporting means comprising an inlet which, subsequent to submersionto the sample extraction depth, is filled with fluid, and a sampleextractor to perform the method which alleviates the disadvantagesconcerning the use of the known pumps and which permits the extractionof intact and representative water samples without allowing theextracted samples to contact the atmosphere during sample extraction.

It has been realised in the invention that this purpose is obtainable inthat the hollow flexible body is held in support means in the form of apressure vessel during lowering to the desired sample extraction depthand filly compressed by means of a pressurised gas inside the pressurevessel, whereupon the pressure in the pressure vessel is caused tochange in such a way that a surrounding fluid seeps into the hollowflexible body.

Due to the fact that the hollow flexible body is fully compressed untilthe seeping of the fluid is effected by releasing the pressure in thepressure vessel it is obtained that the collected fluid sample does notcontact the atmosphere which means that the sample remains intact andhence un-influenced, until it is analysed.

For the performance of the methods, a sample extractor is provided ofthe kind in which the support means are constituted by a leak-proofcontainer in which is placed the compressible hollow flexible body inthe form of a bag of a suitable clean and resistant material, the openend of which is connected to the inlet in an air- and fluid tightmanner, and which container is connected to a hose, at the other end ofwhich means are provided for controlling the pressure between the wallof the container and the outside of the bag, which inlet is preferablyprovided at a bottom end of the container, viz. a removable tightlyfitting plug, to which is fitted the flexible body and which has athrough passage with an embedded one-way valve.

It is hereby possible to lower the sample extractor to the preferreddepth in, e.g., a well, and here extract an intact fluid sample byequalising the pressure in the pressure vessel at the valve, whereby thesurrounding liquid pressure in the well will cause a flow of liquidthrough the one-way valve and into the bag.

In order to avoid the collection of liquid in the gap of the one-wayvalve at the valve seat during the lowering of the sample extractor tothe desired sample extraction depth, the one-way valve seat is oblongand conical, and the plunger is similarly inverse oblong and fitting tothe valve seat, and the valve seat furthermore communicates with apreferably oblique passage in the longitudinal direction in the lowerend of the plug, so that the lower part of the oblong conical plungerprojects into the passage.

The functioning of this embodiment of the one-way valve and the plug isthat there is no cavity in the opening of the one-way valve in whichliquid may collect, because the plunger fills the opening of the one-wayvalve completely. Furthermore the embodiment of the one-way valveensures a very large sealing surface between the valve seat and theplunger. Furthermore the oblique disposition of the passage contributesto ensuring that the liquid collected in the bag via the one-way valveis representative for the level below the surface of the liquid to whichthe sample extractor has been lowered, as during the lowering below thewater table there will be a flow of liquid through the passage, andhence the liquid present in the passage will always come from the liquidpresent at the level to which the sample extractor has been lowered.

In order to prevent the influence of liquid pressure on the plunger ofthe one-way valve, the lower part of the plug may be of a conical shape,hereby the passage is protected and also the end of the plungerprojecting into it, however without blocking the passage.

In order to ensure that there is no air in the bag during the loweringof the sample extractor and during the sample extraction, the upper partof the plunger of the one-way valve, around which the bag is fitted maybe rounded and mutually adjusted in such a way that there are no airpockets present between the mouth of the bag and the top of the plug andsaid plunger in the compressed condition of the bag during lowering forthe extraction of a liquid sample and such that turbulent liquid flowvia the one-way valve into the volume of the bag is prevented.

In order to remove minute undesired amounts of air between the waterlevel in the liquid sample collected in the bag and the top of the bag,the bag may be fitted with a valve at its closed end for the expulsionof air before packing and sending the sample for analysis.

In order to enable the control of the pressure of the fluid whichcompresses the body in the sample extractor, the pressure hose betweenthe container and the valve may be fitted with a double tee fitted witha pressure indicator, a one-way valve with a fitting for connecting to apressure source.

In order to enable the use of the sample extractor for the extraction ofsamples at small distances below a water table, the double tee may beconnected to a valve for the control of pressure, a pressure indicatorand the double tee may optionally be connected via a valve to a sourceof pressure and/or vacuum, whereby the pressure chamber may respectivelybe supplied with pressure for complete compression of the bag duringlowering and vacuum during the actual sample extraction, whereby liquidis sucked into the bag.

It should be mentioned that the method according to the invention aswell as the sample extractor for performing the method may also be usedfor sample extraction in other connections than for the extraction ofsamples in a well sunk into the ground. The invention is furthermoresuitable for the extraction of intact samples in, e.g., lakes, openwells, tanks, including oil separators.

The invention is explained in greater detail in the following withreference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of a sample extractor according to the invention,

FIG. 2 is an exploded detailed side view of a sample extractor accordingto the invention, and

FIG. 3 is a side section of the same lowered into a well during sampleextraction.

DETAILED DESCRIPTION OF THE INVENTION

The sample extractor shown in FIGS. 1 and 2 comprises a sealed container2 in the upper end of which there is a sealed threaded plug 3 with aquick-release connector 9 in which there is connected a pressure hose 4supplied with distance markings 5 in its longitudinal direction. Thepressure hose 4 is connected via a quick release connector 9 at the endopposite the container to a double tee 11 supplied with a valve or aone-way valve which via a quick-release connector 9 is connected to notshown source of pressure or vacuum. A pressure indicator is furthermoreconnected to the double tee which, in the embodiment shown, is amanometer 8, and a blower valve 10.

The lower end of the container is supplied with a screwed-in sealed plug12, the lower end of which is oblong conical, and in the central part ofwhich there is a one-way valve consisting of an oblong conical valveseat 13 and a plunger 15 co-operating therewith, the movements of whichare checked by a pin 14 a projecting into a recess 14 b in the plunger15 in order that flow into the space 16 of the container only ispermitted.

The bottom part of the plug has a crosswise and obliquely upwardsdirected passage 17 which communicates with the lower end of the valveseat, so that the plunger 15 of the one-way valve projects into thepassage 17 without blocking it. The upper part of the plug has a stud 18upon which a bag 22 in a suitable, sterile and resistant material hasbeen fixed by fixation means 20 so that liquid flowing through theone-way valve is led to the inside of the bag. At the upper part of thecontainer 2 there is fitted a weight 24 for overcoming the buoyancy ofthe container when it is lowered below a liquid surface.

The upper part of the plug 12 is rounded at the edge and made to fit arounded shape on the plunger of the one-way valve 15. The purpose ofthis is partly to avoid sharp voids in which air pockets may collectbetween the compressed bag 22 and the parts mentioned and partly tocounteract turbulent liquid flow during the sample extraction.

Before sample extraction by means of the sample extractor, it isprepared in order to compress the bag 22 completely inside the container2, which is performed in that a fluid (e.g., atmospheric air) issupplied under pressure by means of the air valve to the containervolume 16. The compressed air may be supplied to the container volume,e.g., by means of a well-known bicycle pump via the pressure hose 4 andthe one-way valve 7 on the double tee 11.

FIG. 3 shows the sample extractor during the taking of a sample in awell 26. It is presupposed that the sample extractor has been lowered tothe preferred sampling depth, below the water level 28 in the well 26which may be easily determined by means of the distance markings 5 onthe pressure hose 4. The liquid sample is now obtained by opening theaeration valve 10, whereby the pressure in the pressure hose 4 and hencealso in the volume 16 of the container are equalised, and hence also thepressure which compresses the bag 22. The external liquid pressure onthe container and the opening of the one-way valve will cause the liquid30 to flow through the opening of the one-way valve into the bag 22 inaccordance with the equalisation of the pressure in the container, asindicated in FIG. 3.

When the pressure in the container 2 has been completely equalised thebag 22 is completely filled with liquid 30. The sample extractor issubsequently hoisted out of the well 26 and the liquid 30 collected inthe bag is retained by means of the plunger 15 of the one-way valvewhich blocks the connection to the passage 17. The bag 22 containing theliquid 30 may be carefully removed from the bottom of the container 2together with the plug 12, by loosening the latter, so that theextracted liquid sample does not get in contact with the surroundingair. The bag 22 with the plug 12 may subsequently be taken to alaboratory for analysis, alternatively be closed by means of squeezingbelow the plug 12, and the bag containing the liquid sample may be takento a laboratory.

The bag may in a particular embodiment be fitted with a valve 32 at itsclosed end, via which certain minimal amounts of air between the insideof the bag 22 and the liquid sample may be removed, in case suchamounts, against expectations were present during the removal of the bagwith the liquid sample from the container 2.

The container 2 as well as the bag 22, the one-way valve 14, and the airhose are considered to be manufactured in a suitable resistant plasticmaterial which is not dissolved or attacked by aggressive liquids.Furthermore the weight 24 considered to be coated with a similarmaterial. As a particularly suitable material for the manufacture of thebag 22, it may be stated that this may advantageously be made of aTeflon film.

What is claimed is:
 1. A method for the extraction of intact liquidsamples by submersion of a compressible hollow flexible body which isfitted in a pressure vessel having a one-way valve in a lower partthereof and which, subsequent to submersion to a sample extractiondepth, is acted upon to effect liquid entry through an inlet of saidhollow flexible body, comprising the steps of: lowering the vessel withthe hollow flexible body to a desired sample extraction depth, thehollow flexible body being fully compressed by means of a pressurizedgas inside the pressure vessel and with surrounding liquid passingthrough and out of an inlet passage of said pressure vessel as it islowered without admitting said liquid into the inlet of the hollowflexible body during said lowering; changing the pressure in thepressure vessel in such a way that a liquid sample is extracted from thesurrounding liquid by the liquid seeping through said one-way valve andinto the hollow flexible body; and after completion of sampleextraction, hoisting the pressure vessel with said one-way valveblocking contact between the extracted liquid sample and matters outsidethe vessel to retrieve the sample extracted.
 2. A sample extractorcomprising: a leak-proof container having an openable passage forliquid; a compressible hollow flexible body in the form of a bag of aclean and resistant material fitted in said leak-proof container with anopen end of the bag connected to said openable passage in an air- andfluid-tight manner; and a hose, one end of which is connected to saidcontainer and an opposite end of which is connected to a means forcontrolling the pressure between the container and an outer side of thebag; wherein said openable passage is formed in a plug that is removablytightly fitted to the open end of the bag, and wherein a one-way valveis provided in said plug for enabling liquid flow into said bag and forblocking liquid flow out of said bag.
 3. A sample extractor according toclaim 2, wherein said passage extends through said plug for enablingsurrounding liquid to pass through and out of the passage withoutadmitting said liquid into the hollow flexible body, and wherein saidone-way valve intersects said passage without blocking it.
 4. A sampleextractor according to claim 2, wherein the one-way valve has an oblongconical valve seat and a similarly oblong conical the valve seatmatching the valve seat, said valve seat being disposed in the plug insuch a manner that the valve seat communicates with said passage;wherein said passage is longitudinally obliquely oriented in a lower endof the plug; and wherein a lower part of the oblong conical plungerprojects into the passage.
 5. A sample extractor according to claim 4,wherein the lower part of the plug has a conical shape.
 6. A sampleextractor according to claim 5, wherein an upper end of the plug and anupper end of the plunger, around which the bag is fixed, are rounded andmatched such that no air pockets occur between mouth of the bag and theupper end of the plug and said plunger in the bag's compressed conditionduring lowering for the extraction of a liquid sample, and such thatturbulent liquid flow through the one-way valve into the cavity of thebag is avoided.
 7. A sample extractor according to claim 6, wherein thebag is supplied with a valve at a closed end, which enables the removalof undesired air between a surface of the liquid collected in the bagand a top of the bag immediately subsequent to the sample extraction andprior to packing for sending.
 8. A sample extractor according to claim7, wherein the means for controlling the pressure between the containerand the outside of the bag comprises a double-tee to which is connecteda pressure indicator and a one-way valve with an adaptor for connectionto a source of pressure.
 9. A sample extractor according to claim 7,wherein the means for controlling the pressure between the container andthe outside of the bag during use of the sample extractor for takingsamples at low depths below a liquid surface comprises a double-teeconnected to a valve, a pressure indicator, and an adaptor connected toa source of pressure or vacuum.
 10. A sample extractor according toclaim 9, wherein a rate of change of pressure in the container iscontrolled by the valve connected to the double-tee, and hence also thevelocity of the flow through the one-way valve in the plug into the bag.11. A sample extractor according to claim 10, wherein a weight is fittedon top of the container in order to counter-act its buoyancy so that thecontainer, and consequently the sample extractor, may be brought to adesired sampling depth below a liquid surface.
 12. A sample extractoraccording to claim 2, wherein a lower part of the plug has a conicalshape.
 13. A sample extractor according to claim 2, wherein an upper endof the plug and an upper end of a plunger, around which the bag isfixed, are rounded and matched such that no air pockets occur between amouth of the bag and the upper end of the plug and said plunger in thebag's compressed condition during lowering for the extraction of aliquid sample, and such that turbulent liquid flow through the one-wayvalve into the cavity of the bag is avoided.
 14. A sample extractoraccording to claim 2, wherein the bag is supplied with a valve at aclosed end, which enables the removal of undesired air between thesurface of the liquid collected in the bag and the top of the bagimmediately subsequent to the sample extraction and prior to packing forsending.
 15. A sample extractor according to claim 2, wherein the meansfor controlling the pressure between the container and the outside ofthe bag comprises a double-tee to which a pressure indicator and aone-way valve with an adaptor for connection to a source of pressure areconnected.
 16. A sample extractor according to claim 2, wherein that themeans for controlling the pressure between the container and the outsideof the bag during the use of the sample extractor for taking samples atlow depths below a liquid surface comprises a double-tee connected to avalve, a pressure indicator, and an adaptor connected to a source ofpressure or vacuum.
 17. A sample extractor according to claim 2, whereina rate of change of pressure in a pressure vessel is controlled by avalve, and hence also the velocity of the flow through the one-way valvein the plug into the bag.
 18. A sample extractor according to claim 2,wherein a weight is fitted on top of the container in order tocounter-act its buoyancy so that the container and consequently thesample extractor may be brought to the desired sampling depth below aliquid surface.